This paper reports on the use and impact of a negotiated intervention for teacher development adopted for facilitating the teaching and learning in a semester-long fully online graduate course in a tertiary institution in New Zealand. The negotiated intervention strategy, while it begins by exploring teachers’ current practice, is explicit in acknowledging that teachers can expect to change their practice albeit in negotiation with a researcher. This approach therefore moves beyond that of one-off workshops and technical training sessions, which are of questionable value in promoting deep conceptual and practice change. Cycles of formative negotiation assisted the experienced, face-to-face teacher to develop and teach his existing graduate course as an asynchronous online course through ongoing reflection on curriculum, pedagogical practice and assessment. Data were collected through daily observations of the teaching-learning processes, weekly teacher reflective interviews and student interviews. Reflective conversations with the teacher revealed the complexities of working with an experienced teacher to reconceptualise and transform his pedagogical practice and the intellectual, social and emotional changes he faced. The negotiated intervention strategy is relevant in technologically innovative learning environments where the teacher is concerned with responding to a diversity of student knowledge, interests and needs. Implications for employing a negotiated intervention in guiding online teacher action enquiry as development are presented.